Joseph Deiss, the Swiss foreign minister, said that Ambassador Thomas Borer, 44, had been ordered to leave his post at the end of April because he was no longer able to fulfil his duties "effectively and in a dignified manner with due composure and credibility".

The sacking follows reports in two Swiss newspapers, Sonntagsblick and Blick, alleging that Mr Borer had been having an affair with Djamile Rowe, 34.

Sonntagsblick published a photograph of Miss Rowe, a beautician, as she apparently left the embassy clad in boots and mini skirt following one of their alleged nocturnal tristes.

Mr Borer vehemently denied the claims and his wife, Shawne Fielding, 32, a former Texan beauty queen, is standing by him. He has hired Matthias Prinz, a German barrister who once represented Princess Caroline of Monaco, to take action against prying paparazzi.

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He is to sue Zurich-based Ringier AG, which publishes the two newspapers, for invasion of privacy.

Mr Deiss said regardless of whether the story was true or not, he had supported the ambassador throughout the scandal but Mr Borer had not handled it appropriately.

First, the ambassador flouted the minister's express orders "to maintain the utmost reserve" when the scandal broke, and instead made statements to the media.

Then, Mr Borer refused to break off his holiday to return to Berne to discuss the matter with the minister in person, saying he preferred to do this by telephone.

But the last straw was Mr Borer's refusal to vacate the Berlin embassy voluntarily, despite being offered an alternative foreign posting. Mr Deiss said he had launched formal proceedings to remove the ambassador.

The allegations have shocked a nation unused to seeing public figures embroiled in tabloid scandal, but it is not the first time Mr Borer and his have upset the otherwise sedate world of Swiss diplomacy.

Last year, Mr Deiss told the couple to tone down their act after raunchy photographs of Mrs Borer dressed as a pistol-packing Texas cowgirl posing in a low-cut top in the new Swiss embassy in Berlin were published in a German glossy magazine.